The present invention relates to devices and methods for performing automated microwave-assisted chemical and physical reactions.
“Microwave-assisted chemistry” refers to the use of electromagnetic radiation within the microwave frequencies to initiate, accelerate, or otherwise control chemical reactions. As used herein, the term “microwaves” refers to electromagnetic radiation with wavelengths of between about 1 millimeter (mm) and 1 meter (m). By way of comparison, infrared radiation is generally considered to have wavelengths from about 750 nanometers (nm) to 1 millimeter, visible radiation has wavelengths from about 400 nanometers to about 750 nanometers, and ultraviolet radiation has wavelengths of between about 1 nanometer and 400 nanometers. These various boundaries are, of course, exemplary rather than limiting.
Since its commercial introduction, microwave-assisted chemistry has been used for relatively robust chemical reactions, such as the digestion of samples in strong mineral acids. Other early commercial uses of microwave-assisted chemistry included (and continues to include) loss-on-drying analysis. More recently, commercially available microwave-assisted instruments have been able to enhance more sophisticated or more delicate reactions including organic synthesis and peptide synthesis.
In microwave-assisted chemistry, users typically program a microwave apparatus with respect to certain variables (e.g., microwave power or desired reaction temperature) to ensure that the desired reaction (e.g., a particular digestion or synthesis reaction) is carried out properly. Even in robust reactions such as digestion, the proper microwave power and reaction temperature can vary depending upon the sample size, the size of the vessel containing a sample, and the number of vessels. Moreover, different types of vessels can have differing temperature and pressure capabilities, which can be influenced, for example, by the mechanical robustness and venting capabilities of varying types of vessels.
Generally speaking, users must select, and in some cases experimentally determine, the proper microwave power in view of these variable as well as their own judgment and experience.
Although developing parameters experimentally can be helpful, it also raises the possibility of introducing user error into the microwave-assisted reaction. In many analysis techniques, this introduced error will be carried through and reflected in a less accurate or less precise analysis result. In other circumstances, such as during those reactions that require or generate high temperatures and high pressures, a mistake in the experimental or manual setting of the instrument could cause a failure of the experiment or even of the instrument, including physical damage.
As another less dramatic factor, the need to repeatedly enter manual information or carry out manual steps in a microwave-assisted context reduces the speed at which experiments can be carried out. This delay can reduce process efficiency in circumstances where microwave techniques provide the advantage (or in some cases meet the need) of carrying out large numbers of measurements on a relatively rapid basis. By way of example, real-time analysis of ongoing operations may be desired. Therefore, the closer to real time that a sample can be identified or characterized (or both), the sooner any necessary corrections can be carried out and thus minimize any wasted or undesired results in the process being monitored.
Accordingly, a need exists for a microwave apparatus that minimizes or eliminates the risk of user error and that increases the efficiency of microwave-assisted chemistry.